When measuring a device under test with a network analyser, system errors occur—for example, error matching between the input impedance of the network analyser and the impedance of the measurement line—which can falsify the determined measurement parameters if they are not taken into account in the measurement. With regard to a determination of the measurement parameters from which system errors have been removed, these are determined within the framework of a calibration of the network analyser using a calibration module.
For this purpose, the individual ports of the network analyser to be calibrated are each connected in succession to several calibration standards integrated in the calibration module. Then, by means of excitation of the respective calibration standard via the port of the network analyser connected to the calibration standard, the high-frequency wave reflected from the calibration standard is measured at the port of the network analyser and supplied to a calibration method for the determination of the system errors.
The sequential connection of the individual calibration standards of the calibration module to the port of the network analyser to be calibrated is implemented respectively via a control unit integrated in the calibration module. As described in US 2009/0322347 A1, the control unit is therefore supplied, via a separate control line from the network analyser, with the information about the calibration standard subsequently to be connected to the port of the network analyser to be calibrated.
The additional control line complicates the calibration process because an additional line must be plugged in, and for this purpose, disadvantageously requires a more effort-intensive calibration module with an additional port. Especially for applications in which the device under test and therefore also the calibration module is positioned at a relatively large distance from the measuring network analyser, the control line must disadvantageously be reconnected respectively before each calibration process.